1. Field of the Invention
The present invention relates to a method and apparatus for forming structural members from strips or bars of metal in which heating of the center section of the strip or bar in combination with a precision guide die and roll assembly precisely forms the desired shape.
2. Description of the Related Art
Conventional methods for forming structural members in steel include hot rolling techniques. A typical mill receives billets for rolling into shapes at a temperature above 1800 F. and heats them to a temperature of about 2250 F. A structural member having an angle shape can be produced in a roll mill in a nine roll pass by the flat and edging method. This method has the disadvantage of causing significant heat loss in the rolling of thin and narrow structural sections. Structural angles and other shapes in stainless steel below about 1/4 inch in thickness and six inches in width are extremely difficult to produce using conventional technology. Production of structural angles and other shapes in stainless steel below about 1/4 inch in thickness and six inches in width is uneconomical and inefficient.
U.S. Pat. No. 5,435,162 describes a zone heating device for heating the sides of a metal plate during formation of a thickened edge along the edge of the metal plate. An activating means moves a first and second burner relative to the first and second sides of the plate. A forming roll has an axis of rotation transverse to the plate sides for forming the thickened edge.
U.S. Pat. No. 5,454,888 describes a method of warm forming a high strength steel structural member using a starting material of a blank having a tensile strength of at least about 120,000 psi. The high strength steel is formed of carbon and manganese. The stock is warm formed to a temperature of about 800 F. through a tapered die.
U.S. Pat. No. 4,433,565 describes a method for manufacture of a metal profile member by continuously feeding a band along hot shaping and cold shaping procedures. The heating system has the form of a medium frequency induction installation for heating a cross-sectional width of the band at opposite longitudinal edges of the band. The band is passed between pairs of discs disposed on opposite sides of the heated portion. The angle of the discs relative to the band of material is adjusted to cause the heated softened area to be stretched or compacted.
Of general interest are U.S. Pat. Nos. 4,838,062; 4,906,809 and 5,228,324.